Buecherwurm/Lend_Administration.cs

using System.Collections.Generic;

namespace Bücherwurm
{
    class Lend_Administration
    {
        private List<Lending> Lendings {get; set;}

        private List<int> ActiveLendings {get; set;}

        private int NextId {get; set;}

        public Lend_Administration()
        {
            Lendings = new List<Lending>();
            ActiveLendings = new List<int>();
            NextId = 1;
        }

        public void Lend(
            int ItemId,
            string Customer,
            int timeInDays)
        {
            Lendings.Add(new Lending(NextId, ItemId, Customer, timeInDays));
            ActiveLendings.Add(NextId);
            NextId = NextId + 1;
        }

        public void Return(int LendID)
        {
            ActiveLendings.RemoveAll(id => id == LendID);
        }

        public List<Lending> GetAllLendings()
        {
            return Lendings;
        }

        public List<Lending> GetActiveLendings()
        {
            return Lendings.FindAll(lend => ActiveLendings.Contains(lend.LendId));
        }
    }
}